Swales

Swales are a permaculture thing. A swale is a water-holding ditch dug on contour, usually on a slope but not always. The contour bit is very important. If you remember your high-school geography, a contour line on a map joins places at the same height above sea level. In a ditch dug on contour, water stays level in the ditch. Not on contour and it will run out the lowest end.

Huge rainfall events on a slope means water runs off faster than it can soak in. Swales trap the water and allow it to permeate slowly. Water permeates into the soil and facilitates plant growth where it would not be as successful otherwise. Remember the three S‘s of water harvesting: Slow; Store; Soak. Slow it down; store it; let it soak in.

When a swale is dug across a slope, the soil removed is mounded up on the low side of the slope and the mound is planted with suitable plants to hold the soil in place and provide a yield of some sort. In Australia, we call them swales and mounds; in the US they’re often referred to as berms (the mound) and basins (the ditch).

When we bought this property, I didn’t know anything about permaculture. The only spot that was cleared of natural bush was on a slope. The only spot in full sun. The only place to put a vegetable garden and fruit trees. Good drainage, I thought. Yes, but the soil had been introduced. The original sandy soil had been removed (and sold) by a previous owner and the site had been filled with clayey rubbish that water wouldn’t penetrate. If I’d only known—I would have had the whole site swaled and mounded before planting, and be in a far better position than I am now.

So I did a Permaculture Design Course, learned the hard way and had to retrofit. That meant digging individual swales behind each fruit tree, by hand.

The swale behind the orange. It holds about 80 litres of water:

I remember the first major rain after digging the swales, dashing down the back in the pouring rain and being overjoyed to find each small swale full of water.

The swales saved the fruit trees during this past hot, dry summer. Once a week, I filled each of them a couple of times over with the hose.

I used an A-frame to mark out the contours. It’s only small, but just right for the size of the swales I’m digging. I wrote about how I made it here.

There’s an article about water harvesting & storage at the Permaculture Research Institute here.

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This entry was posted on March 19, 2014 at 7:28 pm and is filed under Permaculture, Water. You can follow any responses to this entry through the RSS 2.0 feed.
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7 Responses to “Swales”

I like swales a lot. They’re one of the cheapest ways to hold water on your property. What you describe about the former owners landfill options, sounds a lot like our natural soil, lol. Clay is an awesome growing medium, so long as it stays moist.

An excellent post Bev :). Swales are something that I really want to create but that (like everything else on this property) are much harder to effect than “digging”. Our soil is heavy clay that is cram packed full of rocks and some of those rocks are HUGE. The best option for us is to create hugels on top of the soil with the debris that our clearing has generated (bonus that we don’t have to burn the debris or haul it to green waste 🙂 ) and hope that as the topsoil washes off in the first deluges, that it collects on the hugels. Great information and perfect timing 🙂

Some of my swales have tree roots in them! I just dug around them. So long as the swale is on contour, it will hold the water, tree roots and all.

I just made a new one and the soil was like concrete. I removed what I could and mounded it up on the low side, then covered the mound in short sticks and branches (same length as I use for kindling for the fire…in fact it WAS originally cut for kindling), and as I get more soil from under piles of debris and from the compost heaps, I’ll fill it in between the sticks and gradually build up the mound. You can add small rocks to your mounds.

As the soil in the swale remains moist/wet it will soften and make digging it out easier. I do the rounds of mine regularly and with a short-handled rake, keep deepening them.

That sounds like something that I can do! I kept making excuses as we can’t afford a digger and this “soil” is a bugger to dig but if I chip away at it a bit at a time I reckon we could have swales preserving the moisture in our soil over our long dry summers. Not particularly hot this year just no rain from early December through to last weekend. That’s a heck of a long dry spell! We need to be getting clever with how we garden and making swales is my idea of “clever” on steroids 🙂 Cheers for all of your help Bev. Sometimes you really don’t realise how buoyed I get with your ideas and your shares 🙂